1. Field of the Invention
The present invention relates to an air blowing apparatus and an air blowing method whereby the amount of moisture can be equalized reliably between sheets of paper and within sheets of paper, even in the case of a stack of paper having a large amount of curl.
2. Description of the Related Art
Paper produces deformation due to expansion and contraction immediately after deposition of ink thereon by a printing apparatus, due to differences in the amount of ink solvent in the image region. Deformation due to expansion and contraction of the paper as a result of variation in the amount of moisture in the paper is especially pronounced in systems which perform printing by depositing aqueous ink onto ordinary paper. Furthermore, in double-side printing, there are disparity in image size and position between the images which are formed on the front surface and the rear surface (front/rear image error), as a result of the deformation due to expansion and contraction of the paper after the deposition of ink for front surface printing and before the deposition of ink for rear surface printing. Therefore, immediately after printing, it is necessary to equalize the amount of moisture between the sheets and within the sheets so as to correct or alleviate expansion, contraction, and deformation of the paper, by passing air from the natural environment through the gaps between the respective sheets of paper.
Japanese Patent Application Publication No. 2008-290800 discloses a composition in which the intermediate portion of a stack of paper is gripped from front and rear sides by a pair of pressing members and air is blown onto end faces of the paper stack.
Japanese Patent Application Publication No. 2006-248771 discloses a composition in which a ridge is formed in a stacking surface that supports paper so as to create a peak shape (inverted V shape), in order to correct curl where the paper is curved with a concave shape toward the upper side.
Japanese Patent Application Publication No. 10-297813 discloses a composition in which a paper stack loading table designed to align paper is formed in a tiltable fashion, and furthermore air blowing ports are formed in an outer perimeter wall which surrounds this paper stack loading table.
In a seasoning apparatus which blows air of the ambient temperature and humidity between sheets of paper, in contrast to a simple paper aligning apparatus or paper handling apparatus, it is necessary to blow air simultaneously and uniformly onto the whole stack of paper. In particular, in seasoning of a stack of paper on which images containing a large amount of ink have been printed, if there is a large amount of curl in the end portions of the stack of paper, then the stack of paper may incline toward one side due to the blowing of air, making it impossible to blow air with respect to each individual sheet of the stack of paper. More specifically, as shown in FIG. 13, if curl occurs which bends in the air blowing direction indicated by the arrow in a paper stack 32, then the air flow is not liable to enter into the gaps between the sheets of paper.
In a composition where the intermediate portion of a paper stack is pressed from the front and rear sides by a pair of pressing members, as in Japanese Patent Application Publication No. 2008-290800, as the curl of the paper stack in the air blowing direction becomes greater, there arises a portion of the paper stack which receives the air flow fully and a portion of the paper stack which hardly receives the air flow, and therefore it is difficult to equalize the amount of moisture in the paper stack, even if paper handling is possible. In a composition where an inverted V-shaped stacking surface having a ridge is used, as described in Japanese Patent Application Publication No. 2006-248771, it is difficult to equalize the amount of moisture in the paper stack, even if curl in a concave shape toward the upper side can be corrected in each individual sheet of paper. Even with a composition which uses a tiltable paper stack loading table as described in Japanese Patent Application Publication No. 10-297813, if there is a large amount of curl of the paper stack in the air blowing direction, then there arises a portion of the paper stack which receives the air flow fully and a portion of the paper stack which hardly receives the air flow, and therefore it is difficult to equalize the amount of moisture in the paper stack.